The present invention relates to an apparatus for the release and recovery of living organisms trapped or collected on rotary filters of water pumping stations. The invention relates to an apparatus for use e.g. on filters placed at the inlet of the cooling water circuits of thermal power stations, or on water intakes for urban or agricultural use.
Pumping stations located beside the ocean, lakes and rivers are equipped with drum-type rotary filters, which sometimes have a diameter of 20 meters and their surface is constituted by a system of filter panels having meshes, whose apertures generally have diameters of a few fractions of a millimeter to a few millimeters (3 to 5 mm in the case of French power station water intakes).
Water drawn from the outside towards the inside of the filter, or in the reverse direction contains rubbish and floating material, such as branches, paper, plastic material and the like, which is held back by the filters together with all other living organisms and materials, which are larger than the diameter of the meshes.
The cleanness of the filters necessary for retaining filtering function is ensured by permanent or intermittent cleaning using high pressure water jets located on the upper non-submerged part of the filters. For this purpose, the drum rotates about its axis and the non-submerged filter panels pass in front of a horizontal row of washing means, positioned inside or outside the filter drum, depending on whether filtration takes place from the outside to the inside of the drum or vice versa. The various materials and living organisms stuck to the filter screen are displaced by the water and recovered in a horizontal channel positioned alongside the filtering face.
The filters are cleaned by the action of water jets at a high pressure of approximately 4 to 6 bars. Under these conditions, living organisms are killed or seriously injured by the mechanical shocks to which they are exposed under the action of high pressure water jets and their spraying at high speed against the walls of the inappropriately shaped recovery channel. These organisms are also seriously traumatized by the start of asphyxia resulting from a varyingly long emersion.
To remedy the serious damage to the natural environment and to attempt to provide recovery means which are as advantageous as possible to living organisms, several solutions have already been proposed. Some of them are based on the principle of the recovery of the organisms through the combined use of gravity and a low pressure water jet. However, all these solutions are unusable on certain filters and particularly on those of the drum type, in which filtration takes place from the outside to the inside, because then gravity cannot be used for recovering the organisms.
The object of the present invention is to obviate these disadvantages by supplying a release and recovery apparatus using a stream of water and without using the gravity of the organisms on the rotary filters of the water pumping stations. Such an apparatus is placed in the rising non-submerged part of the filter along a generatrix of said filters and comprises:
on the inside of the filters, a system of two rows of multiple washing jets using water under low pressure, whose nozzles are directed towards the filter panels, so that the jets of the two rows meet one another and cooperate to form a single liquid stream; PA0 deflectors arranged at radial intervals on the outer face of the filter panels; PA0 on the outside of the filters, a channel shaped like a trough for receiving the washing water and recovering the living organisms, whose opening is oriented towards the said rows of washing jets, the edge of the opening being rounded or rotary in its lower part.
It is obvious that the arrangement on either side of the filter panels of the two rows of washing jets and the channel is given here in the case where filtration takes place from the outside to the inside of the filter and that it is reversed in the case when filtration takes place in the opposite direction.
As a result of this arrangement of the apparatus and in particular as a result of the combined effect of the action of the deflectors, the low pressure water jets and the profile of the channel, the living organisms are released from the filter panels and gently displaced at low speed in the channel in a homogeneous liquid stream, without being subject to shocks so that they can be subsequently restored to their natural ambient under better conditions.